Producing solvents from refined coal tar pitch



July 28, 1942- J. E. HARVEY, JR 2,291,319

PRODUCING SOLVENTS FROM REFINED COAL TAR FITCH Filed March 14,` 19413mm/vrom l Patented July 28, 1942 PRODUCING SOLVENTS FROM REFINED COALTAR PITCH Jacquelin E. Harvey, Jr.,rAtlanta, Ga., assignor of one-halfto Southern Wood Preserving Company, East Point, Ga., a corporation ofGeorgia Application March 14, 1941, Serial No. 383,469

Claims. (Cl. 196--53) The present process relates to the production ofvaluable liquids from hydrocarbons, said hydrocarbons characterized bycontent of oxygenated compounds and sulphur.

This application is a continuation in part of my application Serial No.352,668, iiled August 14, 1940, for Production of valuable material,copending herewith, as to all matter common to the two applications.

An object of the invention is the production of refined solvents oflowered corrosivity from hydrocarbons of higher boiling range.

Another object of the present invention is the production of renedsolvents of lowered corrosivity from liquid and solid hydrocarbonscharacterized by content of oXygenated compounds and sulphur.

A more specific object of the present invention is the conversion oftars of aromatic content and fractions thereof characterized by contentof oxygenated compounds and sulphur, substantially in entirety, ifdesired, of the material remaining liquid, into rened solvents ofsuperior solvency and lowered corrosivity.

Other objects of the present invention will become apparent from thefollowing disclosures.

The tars forming suitable starting materials for the present process aretars and their fractions derived from coal and petroleum, includinggases, and are characterized by content of aromatics, oxygenatedcompounds, and sulphur.

Coal tar and fractions thereof will be shown as a starting material ofthe example cited, but it will be immediately apparent that other tarsor fractions thereof characterized by content of aromatics, oxygenatedcompounds and sulphur, serve as suitable starting materials.

Coal tar is a destructive distillate of coal, generally having apredominance of fractions boiling above 190 C. and a typical specicgravity of 1.120. Said tar in its higher boiling range representsmolecular complexes that may be viewed as a multiplicity of ringstructures.

If desired, to the end that coal tar, or fractions thereof, in thesubstantial entirety thereof remaining nally liquid under processconditions, be converted into rened solvents of lowered corrosivity ofthe present process, said molecular complexes may be progressively orstep-wise reduced in size, and, among other things, the presentinvention is predicated on such teaching.

As far as applicant understands the theory of the present invention,same is predicated on the following:

First: by depolym-erizing the molecular com- `plexes in step-wisemanner, they are finally brought down to the refined solvents of loweredcorrosivity of the present invention.

Second: that by impressing reaction conditions on said molecularcomplexes, they are converted into solvents whose solvency is directlymeasurable and usable as opposed to the absence of such characteristicsin the molecular complexes contained in the starting material, and,

Third: to conform to the present invention, said molecular complexesmust be depolymerized under conditions that induce no substantialpercentage of normally liquid products that are other than aromatic. Bythe term substantial aromaticity as used herein and in the appendedclaims is meant that the solvents of the present invention are in theorder of 50% aromatic or more.

Viewed broadly, the present invention provides a process wherein amongother things, coal tar or the like, o r fractions thereof, characterizedby content of oxygenated compounds and sulphur content, is subjected tothe action of hydrogen to lower corrosivity, afterwards to the action ofhydrogen while contacting an oxide catalyst andr a catalyst materialselected from the group consisting of halogens, halids, and derivativesthereof, including substitution and addition products thereof, undercontrolled conditions whereby the high molecular complexes of thestarting material may beV reduced in step-wise manner to provide refinedsolvents of lowered corrosivity and are characterized by lowered andcontrolled boiling range and .directly measurable and usable solvency asopposed to the absence of similar characteristics in said molecularcompleXes containing in the starting material.

By providing the presence of a catalytic material adapted to influencethe decomposition of oxygenated compounds contained in the startingmaterial, the step-wise induction of solvency is enhanced. Includedamong .those catalytic materials adapted to inliuence the decompositionof oxygenated compounds contained in the starting material, are halids,halogens and derivatives thereof` including substitution and additionproducts thereof.

The invention will be understood from the following description ofillustrative steps comprising various methods of securing the objects ofthe invention, when read in connection with the accompanying drawingwherein the ligure is a diagrammatic sketch of an apparatus for carryingout a form of the process of the invention and wherein the nature of thestep carried out in each chamber and the contents thereof are indicatedby legend.

The following examples will serve to illustrate general principles uponwhich the practice of the y present invention is based, as well as theprocess of the present invention.

Example 1.-Coal tar, specic gravity 1.120 and 3% distilling at 210 C.and characterized by sulphur content and content of oxygenated compoundsis treated with hydrogen at 400 C. and 200 atmospheres pressure to lowersulphur content thereby lowering corrosivity. The coal tar of reducedsulphur content is passed through a high pressure reaction vessel at atemperature of 405 C. and a pressure of 300 atmospheres. Flow ofhydrogen is 15,000 cubic feet per barrel tar. The time of contact is onehour and the catalyst molybdenum oxide and tin chloride. Thebeneficiated coal tar flowing from the reactor is distilled to an upperlimit of 210 C. to recover the rened solvent of loweredcorrosivity as adis-A tillate. The residue resulting from said solvent recovery is of amore liquid nature than a comparable cut on the startingmateriaLindicating that the high boiling ends formerly described asincluding multiplicity of rings had either been saturated or partiallysaturated, thus provid-ing the initial step in the step-wise conversionof substantial entirety of the tar remaining finally liquid into therefined solvent of lowered corrosivity'of the present invention. It willbe found that no such percentage of liquidV chainv structures has beeninduced as would preclude production of solvents having an aromaticityof at least substantially 50%, and that no substantial percentage ofcarbonaceous deposition was formed in the reaction chamber. i Unduecoking isundesirable.

The residue resulting from reiined solvent recoveryV may be recycledforconversion to the rened solvent of the present invention orused as anarticle of commerce.

Thus, under the action of hydrogen while contacting an oxide catalystand a catalytic material selected from the group consisting of halogens,halids and derivatives thereof including substitution and additionproducts thereof, the starting material under temperature and pressureconditions chosen from inexcess of 250 C. and atmospheric, respectively,is converted to refined solvents of lowered corrosivity boiling, as anexample, below 210 C., said refinedY solvents being characterized by atleast substantially 50% aromatic content, and being furthercharacterized by being products produced while step-wise reduction of amultiplicity ofY rings is being effected; said solvents are also furthercharacterized by being those productsV iiowing from ring reduction,including in size. The reduction being effected-under coordinated time,temperature and pressure conditions that preclude substantial*deposition, as for instance, 25%. Said carbonaceous deposition referringto any time or period of the process wherein controls are impressed formultiplicity of ring reduction for'nal formation of the refined solventof lowered corrosivity of the present invention.

After formation of the refined solventoflowered corrosivity and theremoval thereof from the parent and beneficiated material, said refinedsolvent may be fractionally cut-as desired, or the cut or cuts may beeffected at the time of recovery from the parent material.

Viewed broadly, the present invention'provides aprocess for subjectingtarsl and fractions thereof boiling substantially above 190 C. andcharacterized by content of oxygenated compounds and sulphur, andderived from coal, petroleum or gas, to the action of hydrogen, asheretofore explained, one or more times, so controlled as to inducesolvent fractions of usable and measurable quality as opposed to theabsenceof such characteristics in the ring multiples contained in thestarting material.

The present invention may be practiced in a discontinuous manner, or ina continuous manner in a high pressure reaction chamber, a series ofreaction chambers, a parallelism of reaction chambers, including amultiplicity thereof.

rather characterized by substantial aromaticityy as heretoforedescribed, and the solventsv so produced may serve as substitutes forthe boilingrange or ranges of benzene, toluene, xylene and the variousnaphthas and plasticizers. Heavy naphthas proposed as solvents arecurrently available having an end point in the order of 360 C. Thepresent inventionprovides for cutting the solvent from the parentmaterial at any point desired with subsequent fractionation into desiredcuts as may be dictated by commercial necessity; residue may berrecycled as aforetaught.

The phase condition of the present process isv liquid phase and is notthat phase that gasiies all starting material. Thev term liquid phase asused herein and in the appended claims may not be technically correct,but isi meant to differentiate from processes-that gasify all materialsprocessed. Y v

The starting materials of thev present process are not circumscribed bylimitation in carbon content, being merely limitedby the nature oftarsand fractions thereof available as the starting material. Tars of morethan usual carbon content may be depolymerized under less severeconditions at rst with severer conditions progressively applied untilmaximum reaction conditions are attained.

Many modes of practicing the present inventionV are possible.Forinstance, tar may be stripped of any percentage of low boiling endsand the residual mass then treated in accordance with the process toprovide the rei-ined solvent of lowered corrosivity of the presentinvention.

Thus, pitches hard or softxare among the Starting materials of thepresent process; also included in the starting materials are thoseoxygenated compounds and sulphur content produced by the petroleumindustry are usable and desirable starting materials.

Those skilled in the art know that hydrogenations proceed at loweredpressures, however commercial recoveries of the refined solvent of thepresent process are best effected at elevated pressures; thus thepresent invention includes use of pressures as high as practicable. Thetime element of treatment in the iirst cycle of hydrogen action is thatperiod necessary for reduction of sulphur content, while in the secondcycle of hydrogen action, treatment may be as short as one hour, ormore, or less.

The starting materials of the present process include tars of aromaticcontent or fractions thereof characterized by content of oxygenatedcompounds and sulphur, at least once refined by hydrogen, or othermeans.

The solvent of the present invention is varied in boiling range andincludes the ranges of any or all of the following:

Product: Boiling range, C. Benzol '78-120 Toluol 100-150 Hi-flashnaphtha 150-200 High boiling crudes 175-360 Heavy naphtha 150-290Plasticizers 16o-360 Instead of controlling the process to provide a lowboiling point of '78 C., as for instance in the benzol shown, processingmay be controlled to produce lower boiling products. Controls of lesserintensity produce solvents of higher initial point, while controls ofgreater intensity produce solvents of lower boiling point.

The solvent of the present process may be characterized by containingfractions boiling at least 150 to 200 C.

Broadly considered, the present process provides a method for convertingtars of aromatic content and fractions thereof including creosote,topped tars, stripped tars and various pitches characterized by sulphurcontent and molecular complexes, to refined solvents of loweredcorrosivity by the controlled action of hydrogen under conditions thatinduce no substantial percentage of liquid chain structures or carbondeposits as heretofore explained.

The catalysts of the present invention are oxides and a catalyticmaterial selected from the group consisting of halogens, halids, andderivatives including substitution and addition products thereof; oxidesof metals of the 6th and 8th periodic groups are usable, however alloxide catalysts may be used. Diflicultly reducible oxides are preferred.

Example 2. It has been discovered when subjecting certain mixtures ofrefined coal tar fractions to the action of hydrogen in accordance withthe present proc-ess for the production of solvents and/or plasticizersthat the formerly accepted teaching that product increment,depolymerization and/or hydrogen absorption are linear functions of thetime, is not followed.

When subjecting a mixture of crude coal tar fractions boilingpredominantly above 250 C. or 275 C. to the action of hydrogen, researchhas disclosed that the newly induced products, depolymerization and/orhydrogen absorption ,are linear functions of the time. As an example,when the above mixture of crude coal tar fractions is subjected to theactionof hydrogen for 2, and 8-hourI periods, the newly 'inducedproducts, depolymerization and/or hydrogen absorption are linearfunctions of the time element.

One of the preferred starting materials of the present process is amixture of refined coal tar fractions boiling predominantly above 355 or380 C. Such a starting material is conveniently the final residueresulting from evaporating coal tar to dryness or substantial drynessand then stripping wood preservative from the distillate. This finalresidue mass of refined coal tar fractions is an especially suitablereiined coal tar pitch to be used as starting material of the presentprocess. However, in contradistinction to the mixture of crude tarfractions boiling predominantly above 250 or 300 C., when the aforenamedpreferred starting material is subjected to the action of hydrogen forproduction of solvents and/or plasticizers, the newly induced fractions,depolymerization and/or hydrogen absorption are not, as described forthe other mixture of crude tar fractions, linear functions of the time.A critical period of treatment by or with hydrogen exists, and which ifexceeded causes loss of newly induced fractions, polymerization and/orlessened hydrogen absorption on certain fractions of the preferredstarting material under treatment.

The critical time element because of the obvious possible variations inthe characteristics of the aforenamed refined coal tar pitch cannot bespoken of as an arbitrary figure. It can be stated, however, that if therefined coal tar pitch were to be subjected to the action of hydrogenfor such a length of time, which for the other crude coal tar fractionswould illustrate that the newly induced fractions, depolymerizationand/or hydrogen absorption were linear functions of the time element,loss of induced products, polymerization and/or lessening of hydrogenabsorption would occur. When treating the refined coal tar pitch by orwith hydrogen, the critical time element is in the order of about threehours.

In the disclosures made herein and in the ap- 'pendedV claims distillateremoval of low boiling portions from the beneiiciated material isconsidered the equivalent of fractional removal by gas movement, solventaction or the like. The converse also obtains.

A refined coal tar pitch selected from the group boiling predominantlyabove, and above, 355 C. and characterized by .sulfur content andcontent of oxygenated compounds is treated with hydrogen at 390 C. and200 atmospheres pressure thereby lowering sulfur content andcorrosivity, at least providing for lowered corrosivity in a finalproduct, the while inducing no substantial percentage of solventlincrement. The refined pitch of lowered sulfur content is passed througha high pressure reaction vessel at a temperature of 430 C. and apressure of 300 atmospheres. The flow of hydrogen is in the order of15,000 cubic feet per barrel feed stock. The time of contact is twohours, and the catalytic material molybdenum oxide and iodoform. Thebeneficiated reiined coal tar pitch flowing from the reactor isdistilled to an upper limit of 300 C. to recover the refined solvents oflowered corrosivity as a distillate. The beneiiciated refined coal tarpitch as iiowing from the hydrogen action last named will be found to becharacterized by lowered oxygen content, specific gravity andviscosity.The residue resulting from said solvent recovery is of a more liquidnature than a comparable cut on the starting material, indicating thatthe high boiling end which may be described as including multiplicity ofring structures had been, at least, either saturated or partiallysaturated, thus providing the initial step in the stepwise conversionVof substantially the entirety of the refined coal tar pitch remainingliquid under process conditions into the refined solvent of loweredcorrosivity of the present process.

The residue resulting from the recovery of the refined solvent from thebeneciated rened pitch may be recycled for conversion to additionalrefned solvents.

In the instance of the solvent recovered to an upper limit of 300 C. asabove described, the solvent cut may be divided to provide solvents ofvarious boiling ranges as may be dictated by necessity. In the event adeep out is taken on the beneciated refined coal tar pitch to providethe solvent and/or solvents of the present process the upper boilingportion of the deep cut may provide a product having inducedplasticizing properties.

When subjectingf a refined pitch to the action of hydrogen for theVproduction of solvents in accordance with the present process, thehydrogen action characterized by solvent increment is controllably heldat or below the critical time period, and if such is exceeded adversereaction will occur. As an example, if the critical time period isexceeded, instead of fractional increment, depolymerization and/orhydrogen absorption being linear functions of the time element, thereverse will obtain. In other words, if the critical time period isexceeded, fractional increment, depolymerization and/or hydrogenabsorption will not be linear functions of the time element, it havingbeen found, among other things, that a period in excess of that which iscritical will provide for loss of fractional increment and /or poly-Vmerization.

The critical time element in the instance of treating the refined coaltar pitch'with hydrogen is in the order of about three hours, andV thepresent process is predicated onl the employment of the critical, orless than the critical, time element.

The refined solvents of lowered corrosivity as being the conversionproducts of the refined pitch are of superior quality and arecharacterized by a preponderance of ring structures.

In the first cycle of hydrogen action that reduces sulphur content, saidreduction of sulphur may be accomplished in the presence of a catalyst.Catalysts effective in the presence of hydrogen are usable, as forinstance, the oxides and/or sulides Vof molybdenum, vanadium, uranium,cobalt, tin, manganese, tungsten, or the like.

In the disclosures herein made the removing of low boiling fractions bygas movement or pressure release is considered the equivalent ofdistillation.

When reference is made to high molecular complexes contained in thestarting material, and when the starting material contains low boilingfractions that are not considered high molecular complexes, it is ofcourse obvious that the high molecular complexes contained in thestarting material are to a certain extent depolymerized by the solventpresent.

It will be seen that by reduction of sulfur content of the materialunder treatment during ,any stage of hydrogen action, the` oxidecatalyst used during subsequent stages is at least partially protectedfrom the effect of the sulfur.

The decomposition influencer which it is desired to have present in thereaction zone is generally taken between 0.1 and 4 or 5 percent, basedon the feed stock, and is preferably taken between 0.1 and 1.5 percent.

Halogens, halids and derivatives thereof are Y employed for catalyticpurposes noted in the foregoing; however, also may be employedsubstances furnishing under the process conditions a halogen or ahydrogen halid. Ammonium chloride Vmay be employed, also halogencompounds of coal tar oils, or the like as for instance the iodides orbromides. Also'may be employed acids such as nitric, sulphuric,sulphonic, formic and acetic.

The addition of the decomposition influencer may be made prior to theentry of the feed stock into the reaction chamber, or at any suitabletime, as for instance after the charging stock has been heated.

When practicing the process, the hydrogen step characterized byreduction of molecular complexes may be carried forward at loweredtemperatures; however temperatures in excess of 350 C. are preferred.The upper limit of temperature usableA is defined as that temperaturethat precludes substantial carbonaceous deposition, as for instancecoking.

An especially attractive form of practicing the present process is tofirst depolymerize the starting material with a solvent, as forinstance, but not in a restrictive sense, a refractory solvent. As anexample of such solvent employment may be mentioned the depolymerizationof the refined coal tar pitch by use of a suitable solvent. The solventmay be employed in quantities up to volume for volume, or more. Afterthe depolymerizing step, the solvent and solute are then subjected tothe action of hydrogen in accordance with the process. Solvents havingat least the power to place a substantial portion of the starting feed,as for instance the reiined coal tar pitch, in solution are preferred.Such solvents may conveniently be secured from the tar or petroleumindustries.

Gas flows may be chosen, as an example, between the limits ofl5,000-25,000 cubic feet per barrel feed; however other ows causing n0adverse reactions may be employed.

Equivalent amounts of compounds furnishing halogen or hydrogen halid maybe employed.

The evaluation of solvent power is conveniently accomplished by findingthe well-known aniline point or kauributanol number. The evaluation ofplasticizing properties is conveniently accomplished by recourse tomethods suggested in chapter VI, The technology of solvents by Dr. OttoJordon, Mannheim,.Germany, translated by Alen D. Whitehead, ChemicalPublishing Company of New York, Incorporated, New York, New York.

Minor changes may be made in the foregoing without departing from thespirit of the invention.

I claim:

1. The process of producing a solvent from the refined pitch produced bystripping high temperature coal tar to at least about substantialdryness, and fractionating the overhead material to recover a liquiduseful as a wood preservative, and a higher boiling fraction boilingpredominantly above 355 C., which process comprises: subjecting saidhigher boiling fraction to the action of hydrogen whereby to lowersulfur content whilst precluding substantial solvent-increment;subjecting the material of lowered sulfur content to the action ofhydrogen at a temperature and pressure in excess of 250 C. andatmospheric, respectively, while contacting as catalytic materials anoxide and a material selected from the group consisting of halogens,halids and derivatives thereof for a period not in excess of about threehours, whereby to avoid loss of newly induced fractions, to provide asolvent.

2. The process of producing a solvent from the refined pitch produced bystripping high temperature coal tar to at least about substantialdryness, fractionating the overhead material to recover a liquid usefulas a Wood preservative, and a higher boiling fraction boilingpredominantly above 355 C., which process comprises: subjecting saidhigher boiling fraction to the action of hydrogen whereby to lowersulfur content whilst precluding substantial solvent increment;subjecting the material of lowered sulfur content to the action ofhydrogen while contacting as catalytic materials an oxide and a materialselected from the group consisting of halogens, halids and derivativesthereof for a period not in excess of about three hours, whereby toavoid loss of newly induced fractions; and fractionating thebeneficiated material to provide low boiling fractions as a solvent.

3. The process of claim 2 with the inclusion of recycling the residue.

4. In the production of a solvent from the refined pitch produced bystripping high temperature coal tar to at least about substantialdryness, fractionating the overhead material to recover a liquid usefulas a wood preservative, and a higher boiling fraction boilingpredominantly above 355 C., which process comprises: subjecting saidhigher boiling fraction to the action of hydrogen whereby to lowersulfur content whilst precluding substantial solvent increment;subjecting the material of lowered sulfur content to the action ofhydrogen at a pressure and temperature in excess of atmospheric and 250C., respectively, while contacting as catalytic materials an oxide and amaterial selected from the group consisting of halogens, halids andderivatives thereof for a period not in excess of about three hours,whereby to avoid polymerization, to provide a solvent.

5. In the production of a solvent from the refined pitch produced bystripping high temperature coal tar to at least about substantialdryness, fractionating the overhead material to recover a liquid usefulas a wood preservative, and a higher boiling fraction boilingpredominantly above 355 C., which process comprises: subjecting saidhigher boiling fraction to the action of hydrogen whereby to lowersulfur content whilst precluding substantial solvent increment;subjecting the material of lowered sulfur content to the action ofhydrogen at a pressure in excess of atmospheric and a temperature inexcess of 250 C. while contacting as catalytic materials an oxide and amaterial selected from the group consisting of halogens, halids andderivatives thereof for a period not in excess of about three hours,whereby to avoid lowered hydrogen absorption, to provide a solvent.

6. The process of producing a solvent which comprises: evaporating hightemperature coal tar to at least about substantial dryness;fractionating the overhead material to recover a liquid useful as a woodpreservative, and a higher boiling fraction boiling predominantly above355 C.; subjecting said higher boiling fraction to the action ofhydrogen whereby to lower sulfur content whilst precluding substantialsolvent increment; and subjecting the material of lowered sulfur contentto the action of hydrogen while contacting as Catalytic materials anoxide and a material selected from the group consisting of halogens,halids and derivatives thereof for a period not in excess of about threehours, whereby to avoid loss of newly induced fractions, to provide asolvent.

7. The process of producing a solvent which comprises: evaporating hightemperature coal tar to at least about substantial dryness;fractionating the overhead material to recover a liquid useful as a woodpreservative, and a higher boiling fraction boiling predominantly above355 C.; subjecting said higher boiling fraction to the action ofhydrogen whereby to lower sulfur content whilst precluding substantialsolvent increment; subjecting the material of lowered sulfur content tothe action of hydrogen while contacting as catalytic materials an oxideand a material selected from the group consisting of halogens, halidsand derivatives thereof for a period not in excess of about three hours,whereby to avoid loss of newly induced fractions; and fractionating thebeneficiated material to provide low boiling fractions as a solvent.

8. The process of claim 7 with the inclusion of recycling the residue.

9. The process of producing a solvent which comprises: evaporating hightemperature coal tar to at least about substantial dryness;fractionating the overhead material to recover a liquid useful as a woodpreservative, and a higher boiling fraction boiling predominantly above355 C.; subjecting said higher boiling fraction to the action ofhydrogen whereby to lower sulfur content whilst precluding substantialsolvent increment; and subjecting the material of lowered sulfur contentto the action of hydrogen at a pressure in excess of atmospheric whilecontacting as catalytic materials an oxide and a material selected fromthe group consisting of halogens, halids and derivatives thereof for aperiod not in excess of about three hours, whereby to avoidpolymerization, to provide a solvent.

10. The process of producing a solvent which comprises: evaporating hightemperature coal tar to at least about substantial dryness;fractionating the overhead material to recover a liquid useful as a woodpreservative, and a higher boiling fraction boiling predominantly above355 C.; subjecting said higher boiling fraction to the action ofhydrogen whereby to lower sulfur content whilst precluding substantialsolvent increment; and subjecting the material of lowered sulfur contentto the action of hydrogen while contacting a catalytic material selectedfrom the group consisting of halogens, halids and derivatives thereof ata pressure in excess of atmospheric and a temperature in excess of 250C. for a period not in excess of about three hours, whereby to avoidlowered hydrogen absorption, to provide a solvent.

JACQUELIN E. HARVEY, JR.

